1. Field of the Invention
The present invention relates to a color filter, obtained by coloring a colored layer with an ink jet method, suitable for a color liquid crystal display and the producing method of the same.
2. Description of the Related Art
Recently, with the development of the personal computers, in particular, the development of the portable personal computers, demand for liquid crystal displays, especially for color liquid crystal displays tends to be increased. Further, bigger liquid crystal displays are in demand. However, the color liquid displays are expensive; therefore, a request that the cost should be reduced has been increasing. In particular, a request that the cost of their color filters, which accounts for a high ratio in the total cost, should be reduced has been raised.
Such color filters, in general, comprise colored patterns of three primary colors of red (R), green (G) and blue (B) so that liquid crystals are operated as a shutter by switching on or off the electrodes each corresponding to the pixels of R, G and B. Thereby, color display can be provided according to light transmission to the each pixel of R, G and B.
The color filter producing method which has been hitherto performed is, for example, a dye method. In this dye method, a water-soluble polymer which is a material for dyeing is first produced on a glass substrate, patterned into a desired shape in a photolithographic step, and then the resultant pattern is immersed into a dyeing bath to yield a colored pattern. This is repeated three times, thereby forming color filter layers in R, G and B.
Another example of the producing method is a pigment dispersion method. In this method, a photosensitive resin layer wherein a pigment is dispersed is first formed on a substrate, and patterned to yield a mono-colored pattern. This step is further repeated three times, thereby forming color filter layers in R, G and B.
Different examples of the method include an electrode positing method, and a method of dispersing R, G and B pigments in thermosetting resins, respectively, performing printing for R, G and B three times, and then thermosetting the resins. However, according to the methods, in any case, the same step should be repeated for three times for coloring the three colors of R, G and B so that problems are involved in that the cost is increased or the yield is lowered due to the repetition of the steps.
In the meantime, the applicant has been investigating a method for producing a color filter, including the steps of using a property changeable pattern forming coating solution containing a photocatalyst and a material having a property changed by the action of a photocatalyst accompanied by energy irradiation to form a photocatalyst containing layer, exposing the resultant in a pattern form to light, so as to form a pattern with the property changed, and then forming a colored layer by such as an ink jet method (Japanese Patent Application Laid-Open No. 2001-074928). According to this method, the property of the photocatalyst containing layer is used to make it possible to form a colored layer easily.
The formation of the photocatalyst containing layer used in such a method is attained, as illustrated in, for example, FIGS. 5A and 5B, by coating a photocatalyst containing layer forming composition 13 onto a base material 1 on which a light shielding part 2 is formed (FIG. 5A) and then drying this photocatalyst containing layer forming composition 13 (FIG. 5B) When the light shielding part is a light shielding part made of a resin at this time, it is necessary to make the film thickness thereof larger than that of any light shielding part made of a metal such as a chromium from the viewpoint of light shielding property and others. Thus, it is necessary to make the film thickness thereof about ten times larger than that of the photocatalyst containing layer. Usually, the applied photocatalyst containing layer forming composition is dried until the film thickness is turned into about 1/100. In this way, the composition is made into the photocatalyst containing layer. Accordingly, when the photocatalyst containing layer forming composition is applied onto the base material with this resin light shielding part formed thereon and then dried, the photocatalyst containing layer is not easily formed in consistency with the shapes of the light shielding part in the case where the light shielding part has a shape perpendicular to the base material. This is because the film thickness of the light shielding part changes abruptly at end portion (i.e., edge) of the light shielding part. In particular, on side face of the light shielding part, the photocatalyst containing layer sometime become thin or is chipped. When unevenness in film thickness or chipping is generated in the photocatalyst containing layer, at the time of using a difference in wettability in the photocatalyst containing layer to apply a colored layer forming coating solution into opening parts made in the light shielding part, for example, the light shielding part having liquid repellency is made exposed in the region where this photocatalyst containing layer is chipped, or the other region. Consequently, the colored layer forming coating solution neither wets nor spreads sufficiently, so that such as white spots or color unevenness may be generated.